Simplify the following expression: $z = \dfrac{-9k}{6} + \dfrac{k}{6}$
Since the expressions have the same denominator we simply combine the numerators: $z = \dfrac{-9k + k}{6}$ Combine like terms: $z = \dfrac{-8k}{6}$ Simplify by dividing numerator and denominator by 2: $z = \dfrac{-4k}{3}$